O-rings are widely used for sealing (seals). O-rings are produced from a material having resilience in order to seal by the pressure generated when crushed. A common material as the material of O-rings is rubber. Patent Document 1 listed below discloses a method of producing O-rings from silicone rubber.
The production method disclosed in Patent Document 1 is a method of producing O-rings by press molding using dies. In press molding, the silicone rubber in the die cavity swells upon press molding and a valley tends to be produced, due to being conducted by heating the dies.
As a countermeasure thereof, the excess silicone rubber other than the volume amount of the O-ring that is the product or the silicone rubber swelled by heat is suctioned by a valley suction part, and subsequently, the valley suction part is cut off. However, it is difficult to cut off to cleanly leave only the product portion, and defects tend to occur. Therefore, with the technology of Patent Document 1, press molding is performed by sandwiching a film having a thickness on the order of 25 μm between the pressing die and fixed side die having a die cavity of the O-ring.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. H10-323845